Intravital Microscopy of Monocyte Homing and Tumor-Related Angiogenesis in a Murine Model of Peripheral Arterial Disease

Abstract

The therapeutic goal for peripheral arterial disease and ischemic heart disease is to increase blood flow to ischemic areas caused by hemodynamic stenosis. Vascular surgery is a viable option in selected cases, but for patients without indications for surgery such as progression to rest pain, critical limb ischemia, or major disruptions to life or work, there are few possibilities for mitigating their disease. Cell therapy via monocyte-enhanced perfusion through the stimulation of collateral formation is one of a few non-invasive options. Our group examines arteriogenesis after monocyte transplantation into mice using the hindlimb ischemia model. Previously, we have demonstrated improvement in hindlimb perfusion using tetanus-stimulated syngeneic monocyte transplantation. In addition to the effects on the collateral formation, tumor growth could be affected by this therapy as well. To investigate these effects, we use a basement membrane-like matrix mouse model by injecting the extracellular matrix of the Engelbreth-Holm-Swarm sarcoma into the flank of the mouse, after occlusion of the femoral artery. After the artificial tumor studies, we use intravital microscopy to study in vivo tumor-angiogenesis and monocyte homing within collateral arteries. Previous studies have described the histological examination of animal models, which presupposes subsequent analysis to post-mortem artifacts. Our approach visualizes monocyte homing to areas of collateralization in real time sequences, is easy to perform, and investigates the process of arteriogenesis and tumor angiogenesis in vivo.

Multiscale Live Imaging Using Förster Resonance Energy Transfer (FRET) for Evaluating the Biological Behavior of Nanoparticles as Drug Carriers

“…Intravital imaging has been developed for the direct observation of biological mechanisms, and it is used to reveal cell dynamics in tissue. 35,41,42 Because intravital imaging enables observation while maintaining normal blood flow, the method has begun to be used for nanoparticle imaging such as visualizing the extravasation of polymeric nanoparticles at the tissue scale. 43 However, no studies have applied FRET for intravital imaging to trace the dissociation fate of nanoparticles.…”